# Third method for generation of spectral holes in chiral sculptured thin films

## TL;DR

This paper introduces a new method for creating spectral holes in chiral sculptured thin films using a two-section design with different dielectric properties, expanding the ways to manipulate polarization-sensitive spectral features.

## Contribution

The paper proposes a novel third method for generating spectral holes in chiral STF devices by using two sections with specific dielectric differences, based on the concept of pseudoisotropy.

## Key findings

- Theoretical validation of the third method for spectral hole generation.
- Design principles involving two sections with same periodicity but different dielectric properties.
- Potential applications in polarization-sensitive optical devices.

## Abstract

The introduction of either a central layer defect or a central twist defect in a periodic structurally chiral material generates circular-polarization-sensitive spectral holes in the remittance spectrums for normally incident plane waves. We propose and theoretically establish here the third method to generate such spectral holes using two-section chiral sculptured thin films (STFs). Both sections of the proposed device have the same periodicity and handedness, but their dielectric properties are different and related in a specific way. The concept of pseudoisotropy is highly relevant for the production of the proposed device.